Clinical trials of drugs. The original drug needs to go through four clinical trials, often more than ten years, involving thousands of patients, in order to comprehensively investigate the effectiveness and safety of a new drug. A generic drug only needs to undergo a small-scale "bioequivalence test" to investigate its absorption speed and degree with the corresponding original drug.
Production technology. Although the effective components of the two drugs are the same, the production processes may be different, which leads to different crystal forms, thus affecting the absorption and stability of the drugs.
Accessories and impurities. Adjuvants play an important role in the stability, absorbability, solubility and oxidation resistance of drugs, and the existence of impurities may affect the curative effect and side effects of drugs. Different brands of drugs also have certain differences in the control of excipients and impurities.